The invention relates to a Laval nozzle having a flow channel, which has a flow cross-sectional profile extending in a convergent-divergent manner.
Laval nozzles of this kind are, for example, used for the purpose of transferring the enthalpy of a working fluid flowing through the Laval nozzle into kinetic energy, i.e. to accelerate the flowing working fluid to as high a speed as possible. The working fluid delivered to the Laval nozzle with subsonic speed is thereby initially accelerated by means of the convergent flow cross-section in the nozzle inlet of the Laval nozzle and thereby achieves the specific sonic speed thereof in the region of the critical, i.e. the smallest, flow cross-section of the flow channel in order to be accelerated further to supersonic speed in the region of a nozzle outlet disposed downstream, which has a divergent flow cross-section. The kinetic energy of the working fluid accelerated in such a way can subsequently, for example, be guided onto turbine blades of an axial turbine and be converted by said turbine into rotational energy.
The Laval nozzles available on the market have however a critical flow cross-section or respectively flow cross-sectional profile of the flow channel, which is constructively designed for a certain mass flow of the delivered working fluid. In the case of a fixed, very narrow flow cross-section, a mass flow can be precisely achieved in the Laval nozzle at a constant pressure upstream of said Laval nozzle. A change in the mass flow therefore accompanies a drop in pressure or an increase in pressure upstream of said Laval nozzle. This is not desirable.
It is therefore the aim of the invention to develop a generic Laval nozzle in such a way that said nozzle can also be efficiently operated at different mass flows of a working fluid.
It is further the aim of the invention to specify a Laval nozzle arrangement as well as an axial turbine comprising a Laval nozzle or such a Laval nozzle arrangement, which can be efficiently operated at different mass flows of a working fluid.